The present invention relates to a wire bonding method and more particularly to a wire bonding method well suited to low-loop implementation.
In wire bonding methods for bonding a ball to a first bond point, the ball neck portion at a tip end of a bonding wire becomes a recrystallized area which is hard and brittle; accordingly, in order to form a wire loop, the wire must be bent from the portion above the recrystallized area. For that reason, it would not be able to respond to the desire for low-loop implementation.
Japanese Patent Application Laid-Open (Kokai) Nos. H9-51011 and 2004-172477 solve the above-described problems. The methods disclosed in these publications takes the following steps: a ball formed at the tip end of a wire is first bonded to a die pad to form a compression-bond ball; next, after raising the capillary, it is moved in a direction opposite from an interconnect wiring (or an outer lead of a lead frame); then, after raising the capillary, it is moved to directly above the pad; the capillary is next lowered, and the wire is pressure-bonded onto the pressure-bond ball; and then, the capillary is moved onto the interconnect wiring, bonding the wire to the interconnect wiring.
In these publications described above, the recrystallized area portion of the wire is bent and bonded onto a pressure-bond ball bonded to the pad; as a result, it would be able to lower the bonding height on the pad and to accomplish low-loop implementation. However, since it is necessary to superimpose wire, doubled, on the pressure-bond ball, there have been inherent limitations to low-loop implementation.